1. Field of the Invention
The present invention is generally concerned with torsional damper devices of the kind comprising at least two coaxial parts disposed to rotate relative to one another.
2. Description of the prior art
This type of torsional damper device is normally incorporated in the design of a clutch disk, particularly for automobile vehicles, in which case one rotary part comprises a friction disk designed to be constrained to rotate with a first shaft, in practice a driving shaft and the motor output shaft in the case of an automobile vehicle, whereas another comprises a hub through which it is adapted to be constrained to rotate with a second shaft, in practice a driven shaft and the gearbox input shaft in the case of an automobile vehicle.
In a specific and relatively simple embodiment, that of the rotary parts of a torsional damper device of this kind which comprises a hub also comprises a hub flange around the hub, disposed transversely relative to said hub and constrained to rotate with it, while the other of said rotary parts, that which carries the friction disk, comprises two rings, usually called guide rings, also disposed transversely relative to the hub, around it and at a distance from one another, with one on each axial side of the hub flange, and constrained to rotate together.
In more complex embodiments the hub flange, detached from the hub, itself forms a part disposed to rotate relative to said hub and/or, apart from the guide rings, and disposed transversely relative to the hub, other flanges which, like the guide rings, extend annularly around the hub.
In all cases there are also employed circumferentially acting elastic means disposed circumferentially between the rotary parts constituting the torsional damper device and adapted to be operative circumferentially between them for part at least of their relative angular displacement, for the purpose of filtering vibration which may arise at any point in the kinematic system in which the torsional damper device is incorporated, extending from the motor to the driven road wheels in the case of an automobile vehicle, together with friction means for damping such vibration.
These circumferentially acting elastic means and, for the most part, these friction means are not relevant in the present context.
The only part of relevance here is the bearing which it is also usual to insert radially between two of the rotary parts constituting a torsional damper device of the kind in question.
More often than not this bearing is fabricated from a synthetic material and at present it is usually of unitary construction, its essential function being to center the rotary parts between which it is inserted relative to one another.
Sometimes it has the additional, but in fact ancillary, function of constituting part of the friction means employed to achieve the required damping.
A general object of the present invention is an arrangement enabling this bearing to be given an advantageous third function, to the benefit of the device as a whole.